Railway traffic controlling apparatus



Sept. 10, 1940.

E. M. ALLEN RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Nov. 5, 1938 6 Sheets-Sheet l VAN R Y wk u NZ R m3 EA m $5 @5 1 m P s Q a m P; n f3 L Sq Q Q3 Q3 m 8% L u Q N m III WQN I l\ N rww FHTv QEN MEN ,QQN Rwww wwmm @J EN 5 fl L 4 my gas w B 8 m %%@N WvQN mv in P 10, 19404 E. M. ALLEN RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Nov. 5, 1938 6 Sheets-Sheet 2 MN W m m u HLS' ATTORNEY 5 wwww mwmv gm? NENm Em Eww .3 9% Qxww L I F be g xww gvw i a? w h, Z w M aw 3w Sept. 10, 1940. 5 ALLEN RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Nov. 5, 1.938 6 Sheets-Sheet 3 lNV ENTOR Allen.

III-5 ATTORNEY p 1 1940- E. M. ALLEN RAILWAY TRAFFIC CONTROLLING APPARATUS 5 0 t Y S R W m m N w M s HT H m umfi wwww fig mag u a I I I 5 w H w Q wwfi w 51 MN Q $5 3% m w v. 3 w w I I EN EN f m m 3 mi Qfiw wwfi $3 mew Q I 1 u I m M? 3N wvww N? n m, m EN gm 3% @wwm wxfi I D b N wfifi j m @sfi 3 H fi w v E Mm D LQ a mm R Q $5 EN mi 3% 3% Em $5 avg 3% www WSQ .r 1. an gm H. llll L 1% F E 5? L Q ha I 5 Rfi REY pt. 10, 1940- E. M. ALLEN RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Nov 5, 1938 6 Sheets-Sheet 6 IN ENTOR I 11/ Non.

ills ATTOR N EY Patented Sept. 10, 1940 UNITED su'mrss entree rarest orrics RAILWAY rnarrrc coNriaoLLrNc arrana'rns Application November 5, was, Serial mean I 24 Claims. (c1. 246-3) 7 this form of my invention-may be illustrated'by My invention relates to railway trafii'c controlling apparatus, and more particularly to centralized trafiic controlling systems for railroads.

In systems of this character, it is customary Q to control the track switches and signals from a central point, usually the train dispatchers office, and to indicate the condition of the trackway apparatus at the office, by means of impulse codes transmitted over line wires extending from the office to each of a plurality of field stations in turn, the same line wires being also used forthe automatic transmission of OS codes indicating the movement of trains past the several stations. 35 One object of my invention is the provision of means for enabling the operator at the control office to selectively render the apparatus at any field station inactive. In accordance with this feature of my invention the signals are arranged to clear automatically to permit train movements past the inactive stationswithout further attention and the transmission of all indication codes except the OS codes from such stations is suspended, thereby greatly decreasing the number of codes per train movement and also decreasing the demands upon the operators time, permitting the connnunicaticn system to be extended to in-v clude a much larger territory than heretofore.

Another object of my invention is the pro- 30 vision of an improved absolute permissive block system for a single track railway'provided with passing sidings, in which the signals clear automatically to permit train movements in either direction. I

vention will appear as the description progresses.

I shall describe two forms of apparatus embodying my invention, and shall then pointout the novel features thereof in claims.

Referring to the accompanying drawings, Figs. 1A., 1B and 1C are diagrammatic views showing trackway apparatus embodying one form of my invention. A complete unit of the trackway por tion of this form of my invention may be illus- 45 trated by placing these views end to end in-order with Fig. 1A at the left, and the system may be further extended by placing additional copies of 1A, 1B and 10 in that order at the right of Fig. 1C, Fig. 2 shows in diagrammatic form a portion a communication system arranged'toc'ontrol apparatus of Figs. 1A, 1B and 1C from a cen- U -.l oiii'ce. Figs. 3A and 3B are diagrammatic views showing the trackway apparatus for a second form oi my invention. A complete unit of all) Other objects, features and purposes of my inplacing Figs. 3A, and 16 end to end'in order with Fig. SA at the left, and the system may be further extended by placing additional copies-of Figs. 3A, 3B and 10 in that order at the right of Fig. 1C.

Similar reference characters refer to similar parts in each of the several views. Referring to Figs. 1A, 1B and 1C,the diagram at" the top represents a stretch of single track railway including a passing siding. Each track is indicated conventionally by a single line, and it is to be understood that the track rails are divided by insulated joints into track sections as v identified by the references '1 with distinguishing numerical prefixes, each track section being provided with the usual closed track circuit having a source of current 33 connected across the rails at one end and a normally energized track relay TR at the other end.

I The point at which the track switch I of Fig. 1A islocated is identified as station No. l of the centralized traffic control system, the circuits and apparatus shown in Fig, 1A being that required for the control of the track switch I, of the head bloclrsignals 2RA and ZLA governing main line train movements over the switch, and of the slow speed signals ZRB and ZLB' governingtrain movements into-and out-of the siding. It isto be understood that the circuits 'and ap-, paratus at station No. 2 at the opposite end of the siding, which are illustrated in Fig. 1B, are

similar except for the fact that corresponding line circuits extend in the opposite direction. Fig.

90 shows the circuits for the intermediate auto- 1 matic signals Ml, H, 112 and i3 located in the single track stretch between two sidings. Since the circuits for the two directions of traffic are similar,it is deemed that a description of' the circuits for one direction will sufiice for a clea understanding of the complete system. Referring to Fig. 1A, the track switch I is provided with the usual dual-control switch machine lSlVl which may be operated by power to normal or reverse by energizing a polarized switch control relay lWR in a corresponding direction. The switch machine has a selector lever EDS by means of Which the switch may be disconnected from the power mechanism and coupled to a hand'ethrow mechanism for local operation'b-ymeans not shown, lever lDS also controlling a relay iWL in such a manner thatrelay lWL is energizedwhen switch l is conditioned for power operation and is deenergized when it is condi tioned for hand operation. The switch machine is also provided with the usual indication circuit controller controlling a polarized switch indication relay IWP which is energized in the normal or reverse direction only when switch i is closed and locked in its normal or reverse position, respectively, as indicated in Fig. 1A. Relays iWR and IWP jointly control two indication repeating relays INWP and iRWP in such a manner, as will be apparent from the circuits shown at the bottom of Fig. 1A, that each normal or reverse repeating relay when energized indicates that switch I is closed and locked in a corresponding normal or reverse position in agreement with the position of the polar contacts of the switch control relay IWR.

The signals may be of any suitable type, but as shown they may be understood to be of the searchlight type, each having a mechanism of the form disclosed in the E. J. Blake Reissue Patent No. 14,940 of August 31, 1920. Each signal mechanism is identified by the reference G. with distinguishing prefix, and each is lighted by a lamp E also identified by a prefix corresponding to the designation of the signal with which it is associated. Each signal which is arranged for full automatic operation is provided with a fixed marker signal M containing a lamp ME.

Under centralized traflic control operation, the track switch and the signals of Fig. 1A are governed manually by means of a group of five control relays, such as the stick relays INWS, IRWS, ZLHS and 20S shown at the right in Fig. 2, which relays are actuated by means of codes transmitted from the ofiice, as hereinafter will be explained. Normally, however, as already mentioned, the manual control apparatus is inactive and the system functions as an automatic block system of the absolute-permissive type. In the inactive condition, the track switch at each station is maintained in its normal position as shown and the code controlled relays NWS and US are held energized over their stick circuits, the remaining code controlled relays being deenergized. Each relay US completes a circuit for energizing a conditioning relay AB, which relay determines the active or inactive condition of the station apparatus. Relay AB is energized, as shown, to render the station apparatus inactive, over a circuit which may be traced in Fig. 2 from the positive or supply terminal B of a suitable local source of current, front contact II of relay 2US, back contacts 12 and I3 of relays ZLHS and ZRI-IS, normal contact I4 of the switch indication relay IWP, relay ZAB to the negative or common return terminal C of the same source.

Referring now to Figs. 1A, 1B and 1C, the apparatus as shown is in its normal inactive condition, and its operation as an automatic block system will now be described in detail, with reference to train movements from left to right.

In Fig. 1A it will be seen that the lamps ZRAE and ZRBE for the signals 2RA and ZRB are lighted and that these signals are both at stop. Signal ZRB is at stop because the circuit for its mechanism ZRBG is open at contact l5 of the reverse switch indication relay lRWP and at front contact 3| of the control relay 2RHS, while signal 2RA is a stop because the circuit for its mechanism ZRAG is open at contact l8 of a normally energized approach relay ZRAR. The polarity of the current supplied to the mech anism G for each main line signal is controlled by a pole changer relay P controlled by the mechanism G for the next signal in advance, mechanism ZRAG, for example, being controlled by the pole changer relay ARAP controlled by mechanism dRAG as shown in Fig. 13, so that when the circuit for mechanism ZRACT is closed, signal ERA will indicate proceed if the advance signal ARA indicates proceed or caution and will indicate caution if signal iRA indicates stop. For each mainline signal a directional stick relay LS or RS is provided, which relay becomes energized when a train passes the corresponding signal at clear, the function of these relays being to maintain the established trafic'direction under certain conditions as hereinafter pointed out. Thus signal ZLA, governing traffic movements from right to left has associated therewith a directional stick relay 2L8, which relay has a back contact is in the circuit for mechanism 2RAG.

Each signal mechanism or group of mechanisms controls an approach locking stick relay such .as the relays ZRAS and ELAS. The circuits for the relays AS are arranged in a wellknown manner as shown, for example, in the Wallace Patent No. 1,959,072, granted May 15, 1934, to provide the usual time and approach locking of the switch andof opposing signals. t is to be understood that these relays are preferably controlled in such a manner that when a signal is manually put to stop, the energization of the associated relay AS is delayed for a measured time interval provided an approach relay AR governed by front contacts of the track relays of an approach zone in advance of the signal is deenergized, this delay being nullified if the signal is put to stop automatically by a passing train or if the approach zone is unoccupied. To simplify the drawings the circuits for the relays AS are not shown in detail further than to indicate by dotted line connections that each is energized only when the corresponding signals indicate stop and the distant signal in the rear indicates stop or caution.

Thus for example, a circuit for relay ZLAS extends from terminal B at back contact 26 or reverse contact 2! of mechanism ALAG, shown at the lower left in Fig. 1B and closed when signal 4LA indicates stop or caution, respectively, thence to- Fig. 1A and over back contacts 22 and 23 of mechanisms ZLAG and 2LBG, closed when signals ZLA and 2LB indicate stop, over other contacts, not shown and then through the winding of relay ZLAS to terminal C. Relay ZLAS when released locks the track switch I by opening its front contact 24 in the circuit for the switch control relay EWR and locks signals ZRA and ZRB by opening its front contact 25 in the circuits for mechanisms ZRAG and 2RBG. I

The track relay ITR 'at its contact 26 completes a circuit for a slow acting repeater relay ITZ, and relays ITZ and ITR have front contacts 21 and 28 in the circuits for mechanisms ZRAG and ZRBG. When the manual control is inactive, as shown, the caution circuit for signal ZRA, which will now be traced, extends from terminal B, back contact 29 of relay iRAP, front contact 30 of relay INW'P, mechanism ERAG, over contacts it to E9 of relays BNWP, ZAB, 2RAR and ZLS, respectively, back contact 3| of relay ZRHS, front contacts 25, Z'l and 28 of relays ZLAS, ITZ and ITR, back Contact 32 of relay IRWP, front contacts 33 and 34 of track relays ZTR and 4TB for sections 2T and AT, contact 35 of the dual selector relav 3W1 for ing from left to right over the tracks of Figs. 1A, 1B and 1C, starting With the condition that the switch 3, contact 36 of the track relay 3'I'R for the switch section 3T, contact 31 of the'approachlocking relay 4LAS, contact 38 of relay AlRAP to terminal C. When switch 3 is reversed, contacts 36 and 31 are bridged by the reverse contact 39 of the switch indication relay 3WP, and it will be seen, therefore, that when switch 3 is reversed, the control limit of signal 2RA extends only to the next signal 43A in advance, but that when switch 3 is normal, as shown, it extends to the opposing signal 4LA and the circuit for signal ZRA is then checked by including therein the front contact 31 of the approach locking relay 4LAS governed by the opppsing signals 4LA and I3.

Since mechanism ZRAG is deenergized normally, the circuit for the pole changer relay ZRAP is normally open at contact 40 of mechanism ZRAG, and the caution circuit for the next signal It in the rear may be traced by placing Fig. 1C at the left of Fig. 1A. circuit extends from terminal 13, back contact 4! of relay 2RAP, mechanism IOG, contacts 42, 43 and 44 of the track relays IOTR, AIOTR and I'IR, contact 45 of relay ZLAS, back contact 46 of relay ERAP to terminal C. It will be seen that the control limit of signal It extends to the opposing signal ELA or 2LB in advance and its circuit is checked by including therein contact 45 of the approach locking relay ZLAS governed by the opposing head block signals 2LA and 2LB and by the distant signal 4LA.

The mechanism for signal I0 is therefore in a position to indicate caution, but this signal is approach lighted and its lamp [0E and also the marker lamp IOME are normally dark, the cir- 'cuits for these lamps being open at contact 47 of an approach lighting relay IUAE and at contact 48 of relay HP associated with the opposing signal H, as will be apparent from Fig. 1C. The circuit for relay MP is, however, completed by mechanism IEBG at its contact 49 so that the clear circuit for the next automatic signal l2 inv the rear is closed from terminal B, through the winding of relay HIAE, contact 50 of relay lllP, back contact 5d of the opposing directional stick relay I IS, front contacts 52 and 53 of track relays I [TR and IZTR, mechanism IZG, contact 54 of relay HJP to terminal C.

Mechanism IZG therefore is normally in the clear position, but this signal is also approach lighted and the circuits for lamps HE and IZME are open at contacts 55 and 56 of relays IZAE: and I3P. The circuit for relay HP is closed by mechanism IZG at its contact 51 and relay IZP is energized to prepare the clear circuit for the next signal 4RA in the rear of signal l2. By placing Fig. 13 at the left of Fig. 1C, this circuit may be traced from terminal-B, relay I2AE, contact 58 of relay IZP, back contact 59 of the opposingdirectional stick relay I38, contacts 60, BI, 62 and 63 of the track relays I3TR, AI3TR, 3TH, and. the repeating relay 3T2, contact 64 of relay 4LAS, back contacts 65 and 66 of the signal control relay 4RHS and of the opposing directional stick relay 4L8, back contact 67 of the approach relay 4RAR, front contacts 63 and '55 of relays 4A3 and 3NWP, mechanism 4RAG, contact 10 of relay [2P to terminal C.

Signal 4RA is lighted by a lamp having a circult similar to that shown for lamp ZLAE in Fig. 1A for the similar signal ZLA and signal 4RA will, therefore, indicate stop, its control circuit being open at contact 67 of relay 4RAR.

V I shall now trace the progress of a train movtrain occupies section 4T. Relay 4TB, and consequently relay 4RAR will be released, completing the circuit for mechanism 4RAG at contact 61 so that signal tRA will indicate clear. If now the train enters section 3T, contacts 62 and 63 of relays 3TB and 3TZ in the circuit for signal 4RA will open, and consequently relay IZAE which is included in series in that circuit will be released. The circuit for mechanism 83G, which extends from Fig. IE to Fig. 10 at the right, and is similar to that for mechanism 8 0G already described, will be open at contact 7! of relay 3TB, and contact 72 of mechanism [36 Will be open so that relay I3P is released. It follows that contacts 55 and 56 of relays lZAE and 53F are both closed, completing a circuit to light the lamps IZE and EZIWE, causing signal it in advance of the approaching rain to indicate clear. As the train proceeds,

the opening of contacts 6i and 172 of relay AISTR and of contacts 69 and it of relay E3TR, respectively, will maintain this condition until the train enters section l2T, whereupon the closing of back contact 74 of relay lZTR completes a pick-up circuit momentarily over front contact 15 of relay HP to energize the directional stick relay HS. Relay 62TH. at contact 53 opens the series circuit for mechanism lZG and relay IUAE. Mechanism I2G releases and by opening contact 51 releases relay I2P. Relay 52F upon releasing completes the stick circuit for relay IZS at back contact 75, and at its back contacts m and. 58

prepares the caution control circuit for signer I 43A including contacts 76 and T! of relay I2S, which circuit will be completed when the train vacates section 131.

Since relay ESP is released, its front contacts 78 and E9 in the circuit for mechanism HG are open and since the front contacts of relay its are also open, it follows that mechanism l l G is deenergized, its contact 39 is open and relay HP is released, and contact 48 of relay MP in the circuit for lamps ME and ltME is closed. When the train enters section lZT, the release of relay JAE therefore completes the lighting circuit for "signal It at its contact 47, causing signal It in cludes the front contacts 83, t4 and 85 of the track relays HTR, ltlTR and AlllTR is opened,

and relay ZRAR releases to complete at contact E8 the caution circuit for mechanism ZRAG already traced. Signal ERA therefore is caused to indicate caution, and contact closes, energizing relay ZRAP to reverse the pole changer contacts and 46 to change the indication of signal it fromcaution to clear. Relay ZRAS now releases, its circuit being opened at contact 86 of mechanism ZRAG and also at contacts Bl and 49 of mechanism 5 Relay 2RAS opens contacts 3S and 39 in the circuits for the opposing signal 'mechanisms ELAG and tLAG, and also opens contact 90 in the circuit for relay lRAR, and contact at in the circuit for relay IWR.

When the train enters section lilT, mechanism MG and relay HlP become deenergized and the directional stick relay its becomes energized, the circuit for relay its being similar to those for relayi'zS alreadytraced.

When the train vacates section vH'I, current of reverse polarity is supplied to mechanism IZG over back contacts M and 5B of relay HEP and front contacts 32 and 93 of relay its, so that mechanism \IZG assumes the caution position.

Contact 5i of mechanism EZG closes, energizing relay HEP which again prepares the clear circuit for signal lRA in the rear and by opening back contact it releases relay I2S..

When the train enters section AIDT, the circuit for relay IRAR in advance of the train, as will be seen by placing Fig. 13 at the right of Fig. 1A, is opened at contact 9% of relay AEBTR in Fig. 1A, since contact 230 of relay ZRAS which also connects terminal B to this circuit is now open. Relay GRAR therefore releases, and at .contact 51 completes the circuit for mechanism l-RAG to clear signal LRA, provided the single track stretch in advance of that signal is unoccupied. Mechanism 4RAG upon becoming energized closes contact 95, thereby energizing relay 4RAP to operate contacts 29 and 38 to change the polarity of the current supplied to mechanism ZRAG from reverse to normal. Mechanism ZRAG therefore becomes energized in the normal direction, causing the indication of signal ZRA to change from caution to clear.

Nhen mechanism iRAG becomes energized, its contact 96 opens the circuit for relay ARAS, and contacts 91 and $8 of mechanism 2RAG in the circuit for relay lRAS are opened when signalZ-RA assumes the clear position. Relay iRAS opens contacts 99 and Hill in the circuits for the opposing signal mechanisms lLAG in Fig. 1B and MG in Fig. 1C at the right of Fig. 1B. This mechanism KEG therefore assumes the stop position, releasing relay BF and causing the mechanism HG for the next intermediate signal II to move from clear to stop, and releasing relay HP to open the circuits for the opposing head block signal such as signal ZLA at the righthand end of the single track stretch in advance thereby extending the portion of track in which the traffic direction from left to right is established to include the single track stretch at the right of signal flRA. Relay 4RAS also opens a contact in the circuit of a relay similar to relay IWR for controlling the switch machine 3SM.

When the train enters section IT, signal ZRA again returns to stop, relay ZRAP releases and relay ZRAS becomes reenergized. Switch I, however, remains locked because contact I06 of relay ITR in the circuit for relay IWR is open, and the closing of contact 9!, and likewise the closing of contacts 88 and 89 of relay ZRAS in the circuits for the opposing signal mechanisms 2LAG and lLAG, and the closing of its contact 9!! in the circuit for relay GRAR, is without effect at this time. Relay ITR at back contact IIB completes a circuit for the directional stick relay.

2RS which is closed momentarily from terminal B, back contacts I01, I08, I09 and N0 of relays 2L3, ZLAP, ZLBP and ITR, front contact III of relay 2RAP to terminal C. Relay ZRS becomes energized and completes a temporary stick circuit which is the same as that just traced except that it includes the front contact H2 of relay 2R8 in place of contact III. Relay 2RS opens contact I I3 in the circuit for the opposing signal mechanism 2LAG. Relay ZLAR releases when the train advances to section 2T, and closes contact H4 in the circuit for mechanism ZLAG. It will be seen that relay 2RS functions in such a manner as to prevent the circuit for mechanism ZLAG from becoming energized in response to the release of relay ZLAR when that relay is released by a train moving from left to right.

Relay ZRS is held energized as long as relay ZLAR is released by a stick circuit which includes its own front contact l I5 and back contact H6 of-relay 2LAR.

When the train vacates section AIUT, mechanism IOG in Fig. 1C at the left of Fig. IA becomes energized in the caution position, as shown, and relay HIP becomes energized, releasing relay IDS and causing mechanism I2G to assume the clear position, as shown, so as to permit a following train to pass through the single track stretch under permissive control in accordance with the usual practice in systems of this character.

When the first train enters section 3T, signal fiRA returns to stop, relay lRAP releases and relay RAS becomes reenergized, and when the train enters section AIBT, relay lLAR releases. It is to be understood that the circuits for relays dLS and IRS are similar to those for relays ZRS and ZLS, respectively, and it follows that relay ERS picks up when the train enters section 3T and is held energized by relay tLAR as long as that relay is released. It follows, therefore, that the circuit for signal ALAG is held open at contact II! of relay lRS as long as relay ALAR is held deenergized by a train moving from left to right, and the closing of contact N8 of relay lLAR in the circuit for mechanism ALAG is rendered ineffective.

When the train vacates section 3T, the circuit for relay ZLAR is completed from terminal B at contact ill of relay lLAS over contacts 993, IM and Hit of relays ZiTR, 4TB and 2TR through relay ZLAR to terminal C, and therefore relay 2LAR becomes energized and relay ZRS releases. Similarly, the circuit for relay iLAR is completed at contact M of relay IETR when the train vacates section EZT, and then relay iLAR becomes energized andrelay 4L6 releases.

It will be seen, therefore, that in accordance with the present invention a given direction of trafiic when once established by a train is main tained past inactive sidings as well as through the single track stretches.

It will be seen that the trafiic direction from left to right is maintained by relay 2R3 until the train vacates section 3T, and by relay lRS until the train vacates section IZT just as it is maintained by relay il -S, associated with the automatic signal iii, until the train vacates section iT. Under inactive control, with relays ZAB. and AAB energized, signals ZRA and ARA may be employed as permissive stop and proceed signals like signals iii and I2. Accordingly, these signals are provided with markers M having lamps ME. The circuit for marker lamp ZRME may be traced in Fig. 1A from terminal B over contacts H9 and 129 of relays ZAB and ZRS, lamp ZRlVlE to terminal C, the circuit for; the marker lamp QRME, not shown, being similarly controlled by relays lAB and ABS.

In the foregoing I have traced the movement of a train from left to right from a left-hand section 3T through the successive track sections extending to a similar section 31 of an inactive passing siding at the right. The circuits for the opposite direction are similar, and the movement of a train from right to left may be similarly traced from any section ET to a similar section IT of the next siding to the left, as will be apparent from the drawings.

There remains to be considered the effect of opposing train movements upon the'system. It has already been pointed out that a train moving from left to right upon entering section IIT releases the reproach relay 2RAR, which relay by closingcontact I8 causes the second signal ERA in advance to assume the caution position and signal iii directly'in advance to indicate clear, and that relay ZRAS is released and opens its contact 89 to hold signal 4LA at stop. Similarly, when an opposing train approaching the same siding and occupying the single track stretch at the right of the siding enters section iET, contact "is of relay IZTR opens to release the approach relay ILAR, and the latter relay by closing its contact II 8 completesthe circuit for mechanism iLAG so that signal ILA assumes the caution position and its distant signal It indicates clear, and relay 4LAS is released and opens its contact 3? to hold signal ZRA at stop. It is evident from the circuits as already described that signals 2RA and lLA at the oppositeends of the siding cannot both be cleared at the same time, and that the train which first enters the adjacent approach zone will take precedence, and also that adequate stopping distance for the opposing trains may readily be provided. It will also be seen that similar conditions prevail in the case two opposing trains approach a single track stretch at the same time, and that signals RA and 213A at opposite ends of the single track stretch cannot be both be cleared at the same time It will be apparent from the foregoing that under the inactive control condition the operator the control oifice is relieved of the usual duty of manually clearing each head block signal in order to permit the movement of trains through the controlled territory, and that manual supervision is not required unless meeting points for opposing trains or passing points for train moving in the same direction are to be arranged.

I shall next describe the operation of the apparatus under manual control. The communication system may be of any suitable type, but as herein disclosed it is to be understood to be similar to the Time Code system as disclosed in a ccpending application, Serial No. 600,786, filed March 23, 1932 by Lloyd V. Lewis, for Remote control systems, which corresponds with British Patent No. 415,787, issued September 3, 1934. In this system, the apparatus at the control ofiice includes a plurality of control panels, one foreach field station, each including a group of levers as indicated in the left-hand portion of Fig. 2,-

for controlling the corresponding station devices,-

together with indication lamps for indicating the condition of these devices. A track diagram is also provided as indicated at the top in Fig. 2, containing a plurality of lamps'for indicating train movements through the territory. The code control of the switch and signal stick control relays at station No. 1 by the levers of the corresponding ofice panel, and also of the lamps of that panel and of the corresponding portion of the track diagram by the indication relays at station No. 1, is indicated diagrammatically by direct wire connections in Fig. 2, in order to illustrate the operation of the various devices in a simple manner. It is to be understood that the.

devices at station No. 2 are similarly controlled and also that the station apparatus as shown in the Lewis application and patent has been modified by the addition of the active-inactive conditioning relay 2AB anditsrepeating' relay 2ABP.

The code sysetem operates in the following manner: To send a control code to station No. 1,

the operator first moves the control levers IWK, 2GK, etc. of the correspondingpanel as required and then momentarily operates a starting key ISK. The latteroperation initiates the'transmission of a code containing selecting elements for selecting station No. 1- and function elements identifying the position of each of the levers of the corresponding panel. The selecting elements cause the momentary energization of a delivery relay ID, thereby-operating thestation stick relays in accordance with the function elements'of the code, that is, to positions corresponding to the lever positions. Thus, for example, the operator may restore the apparatus at station No. 1 to the active condition byop'erating key ISK when the levers IWK, 2GK and ZUK occupy the positions shown in Fig. 2, in which case the energization of relay ID in response to the operation of key ISK will merely open the stick circuit for relay 2US at back contact I2I to effect the release of that relay, thereby deenergizing relay 2AB by opening its circuit at contact II. The operator'may also send a single code, for example, which will not only restore the apparatus at station No. '1 to its active condition but will also reverse switch I and clear signal ZRB to permit a train moving from left to right to enter the siding over switch I, provided the train is at some distance from the switch so that the approach relay 2RAR is energized. In this case levers IWK and ZGK are moved to the right and key ISK then operated to energize relay ID momentarily. Relays INWS and 2US will release due to the opening of back contacts I22 and I2I of relay ID. Relays IRWS will pick up over front contacts I23' and I24 of relays ID and IIWP, and relay 2AB will release dueto the opening of contact II, completing a circuit over contacts I 25 and I26 of relays ID and 2 AB to and I2'I of relay ID.

Referring now to Fig. 1A, it will be seen that in response to the last mentioned code, relay IWR becomes energized in the reverse direction over front contact I28 of 'relay IRWS and back contact I29 of relay INWS, and'th'e left-hand contact I30 of relay IWR opens,

releasing relay I and thereby opening con-' tact I6 in the circuit for mechanism ZRAG, therebyprev'enting the actuation of that mech-' anism in response to the closing of front contact SI of relay ZRHS'. The closing of the righthand contact I 3| of relay IWR causes the switch machine ISM to operate switch I to reverse, and when the switch. becomes locked .in' that position, relay IWP becomes energized in the'reverse direction completing the circuit fo r relay IRW'P at its rright-hand contact I32. Relay IRWP picksup and completes the caution or slow speed controlcircuit for signal ZRB, which may be traced fromterminal B, front contact 32 of relay IRWP, over front contacts 28, 21, 25, 3I'and I5, mechanism ZRBG and back contact 30 of.

relayINWP, to terminal C, so that signal 2RB will display the proper slow speed indication to permit the approaching train to enter the siding.

If the operator should inadvertently attempt toeifect these operations after the approaching train had released; relay 2RAR and thereby 15 cleal'ed signal 2R5, it will be seen that relay ZRAS will have been released by mechanism ERAS and consequently relay IMP in Fig. 2

will be released, the circuit for the latter relay 3 being open at contacts 533 and ltd of relays 1 opened momentarily at front contact H of relay ZAB being closed again over back contact Ill and front contact of relay 2RHS, so that the train is permitted to continue over the established route.

In either case, when the train enters section ET; the signal is put to stop by the opening of contact 23 of relay ETR in the circuits for mechanisms ZRAG- and'ZRBG, relays iTZ-and ERHS being also released by the opening of contacts 26 and E35 of relay lTEt.

The release of relay ERI-IS causes the signal to remain at stop after section ET is vacated, but as-explained in the Lewis application and patent hereinbefore referred to, this relay may be reenergized by code after relay i-TZ releases and closes contact its in order to clear the signal for a following'train, or relay ZRHS may be held energized to permit the signal to clear automatically by sending a code to energize relays ZUS and so as to close contact it?! of relay EUS. In this case, relay 21 5 is not,

operated in response to the energization of relay ZUS because its circuit is held open at contact i3.

"The station apparatus maybe restored to its inactive conditions as shown by operating key ISK with levers l'vv'ii'and normal, as shown, and with lever EUK closed, thereby energizing relays ENWS and 2US and releasing relays ERWS and ZRHS or: ELI-IS, if energized. If the track switch is reversed, it will be restored to normal and relay 2A3 will become energized when the normaL'contac-t it of relay lWP closes.

,It' will be clear from the foregoing that the stationapparatus may be placed in the active or inactive condition at will by the operator, subject to certain restrictions, so as to not interfere with train movements. With the apparatus in the active condition, the operator has full control over the switches and signals but it will-be apparent'that the usual time and approach locking protection and the checking of opposing signals is eifective not only under this condition but also when the apparatus has been restored to its inactive condition and the clearing of the signals for either direction is effected automatically.

It may be desirable at times, as for example, in case of a failure of the communication system, to restore the station apparatus to its inactive condition by local means, and to illustrate this feature a push button EPB is provided in Fig. 2. As will be apparent from the drawing, push button EPB when operated will cause the energization of relays iNWS and ZUS in response to the closing of its front contacts E38 and H39, while the opening of back contact E39 ofpush button EPB will cause relay ZLHS or ZRHSto release if energized, and the opening of back contact Mil of relay lNWS will cause relay. lEWS'to release if that relay is energized. It will be clear therefore that push button EPB when operated will cause the apparatus to assmne its inactive condition as shown. Furthermore, the push button EPB may be replaced if desired by a relay which is operated automatically in the event of a failure of the code line, such relays being shown, for example, in the Kemm rer Patent No. 1,940,913, granted December 26, 193-3, and in the Baughman Patent No. 2,011,237, granted August 13, 1935, in which case the operator may also render all stations inactive manually by merely opening the code line at the control ofiice.

It is to be understood that the transmission of indication codes by the field stations is effected in a manner generally similar to the transmission of control codes as above described, each code including elements for selecting the o ifice panel assigned to the sending station, and other elements each of which is effective to light a particular indication lamp at the office if the corresponding indication contact at the sending station is closed, or to extinguish such lamp if the contact is open. An indication code is initiated either by the momentary energization of a wire marked start in Fig. 2, or by means, not shown, acting in response to a change in position of any of the energized indication contacts, as explained in the Lewis application and patent hereinbefore referred to. Thus, for example, if track section becomes occupied, back contact Ml of relay lTR will close to initiate a code to light the track indication lamp iTE, as indicated by the dotted line connection in Fig. 2, and when section iT is vacated, another code will be initiated to extinguish lamp iTE. Each of these codes includes a switch indication element controlled by a circuit which includes front contact H32 of relay iN'WP and it follows that the normal switch indication lamp INE is lighted as long as switch l is closed and locked in its normal position in correspondence with relay WIR. The similar circuits governing the signal indication lamps ZLE, ENE and BEE, and the approach 2393. are each'normally open at back contact of relay ZAB, and when the apparatus is in its ina condition, as shown, each of these lamps re ains dark. It is to be understood that the opening or" back contact ids prevents the initiation of indication codes in response to a change in position of any of the contacts in series therewith, such as contact i l-d of the approach relay ZRAR or contact M5 of the signal mechanism ZRAG. ont contact t lt of relay ZAB, however, provides starting circuit closed momentarily over the back contact M? of relay ZABP when relay picks up, which initiates a code extinguishing the signal indication lamp when lighted, and the subsequent closing of back contact Ms when relay 2A3 is released initiates another code and ccrnpietes circuits over contact Hi3 and over one or both of the contacts Hi5 and m3 of mechanisms ZRAG and ERBG to restore the signal indication light to correspond with the condition of the signals. It will be seen that this arrangement provides a distinctive indication of the position oi relay ZAB, the signal and approach indication lamps being dark when the station apparatus is in the inactive condition, while lamp ZLE, ENE or litE is lighted and lamp 2RAE is rendered responsive to the condition of relay ZRAR when the station apparatus is in the active condition. Relay 2A3, however, preferably does not govern the circuits for the switch indication lamps lNE and IRE for the reason that when the station is inactive, these relays do not initiate codes as long as'the apparatus is in order and the track switch remains locked andit is desirable to retain the switch indications so that the operator will be promptly advised if any defect develops causing the release of relay lN'WP, so that the defect may be more promptly corrected.

It will be seen therefore that station No. 1 in the inactive condition is simply an OSing point for reporting the passage of trains. understood that generally the movement of trains through the successive switch sections such as section iT Will be recorded on a train graph at the ofiice, as explained in the Lewisapplication and patent.

The apparatus at station No. 2 may control the apparatus of the second oflice panel in a similar manner, but with the sidings closely spaced an OS indication from one end only may sui'lice. The circuit for lamp 3TE, for example, may be controlled over a back contact of the corresponding relay iAB, in which case both lamps 3TB and GLAE will remain dark when a train passes station No. 2 in the inactive condition, thereby still further reducing the number of codes to be transmitted.

I shall now assume that there are two trains approaching from opposite directions, that the apparatus is in the inactive condition as shown, and that the operator is required to effect a meet at the siding of Figs, 1A and 1B, the train moving from right to left taking the siding. It will be evident that signal ZRA will clear automatically and that the train moving from left to right may pass signal ERA at clear without any action by the operator who will, however, be required to send a code to put station No. 2' in the active condition, which code will also serve to reverse switch 3 and to then clear signal 4LB. This code will be followed immediately by an indication code from station No, 2, indicating that switch 3 is in transit, and a second indication code will be transmitted when switch 3 reverses and signal QLB clears. A third indication code will be transmitted when the train passing signal 411B enters section ET, and a fourth when the train vacates that section. The operator will send a second control code to restore station No. 2 to the inactive condition as soon as he is informed that the train entering the siding has vacated section 3T, whereupon an indication code indicating that condition will be transmitted and signal 4RA will clear automatically for the opposing mainline train. An indication code will be transmitted from station No. 1 when the train moving from left to right enters section HT and another when it vacates that section. As soon as the last named code is received, the operator will send a third control code to put station No. 1 in the active condition, this code also serving to reverse switch I and to clear signal ZLB, which code will be followed by four indication codes indicating re spectively that switch '8 isin transit, that it is locked reverse and signal ZLB has cleared, that the train governed by signal ZLB has entered section ET and put that signal to stop, and that that train has vacated section iT. Upon receipt of the last named indication code, the operator will send a fourth control code restoring station No. 1 to the inactive condition'and this in turn will be followed by an indication code from that station. No further action on the part of the operator is required-to complete the movement of the'tw'o trains out of the controlled ter- It is to be ritory. On the other'hand, if all the remaining stations were active, as in centralized trafllc control systems, as heretofore used, the operator would be required to send a control code to each such station to reverse the direction of traffic and to clear the signal at that station and each such code would be followed by a corresponding indication code indicating the clearing of the signal.

The advantages of the inactive control are self evident. It may be shown, for'example, that the number of codes required to move trains through a territory of the usual extent, with all stations active as has heretofore been the practice inthis art, will be from four to six times as great as when all. stations are arranged to be normally inactive as above described and the operator is required to send codes only when meets are to be effected, and it will be seen that the volume of traffic which the system can control is correspondingly increasedby thepractice of my invention,

I shall now describe the second form of my apparatus as illustrated in Figs. 3A, 3B and 1C. This differs from 'the first form principally in that the head block signals ZRA, 2LA, 4RA and ALA, and the intermediate signals I0, II, E2 and I3 are normally clear when the station apparatus is in the inactive condition, while in the first form, the signals are cleared only when a train is approaching. It is to be understood that the circuits are similar to those hereinbefore described except forsuch modifications as are required to provide for normal clear operation, and these modifications will be described as the description proceeds,

Starting with the assumptions that relays ZAB and 4AB'are energized so that the stations are in the inactive condition and that a train moving from left to right occupies a left-hand section 3T, by placing Figs. 10' and" 3A in order at the right of Fig. 3B, it will be seen that the circuit for mechanism I3G is open at contact H of relay 3TB and consequently the circuits for mechanisms HG and ZLAG are also open and the opposing signals l3, H and 2LA in advance indicate stop. Signal I2 is at clear, as shown, and assuming signal ZRA in advance to be at clear or caution, signal l will be at clear. The circuit for mechanism illG may be traced from terminal B, contact 46 of relay 2RAP, Fig. 3A, contact I49 of relay ZLS, the closed front contact 45 of relay 2LAS, the closed back contact i50 of mechanism 2LAG, contacts 44, 43 and 42 of relays ITR, AIOTR and IIJTR, mechanism IUG, contact 4| of relay 2RAP, to terminal C. In order to consider conditions in advance of signal ZRA, drawings 33 and 10 may be placed in or der at the right of Fig. 3A, and it will then be seen thatthe circuits for signal 4RA are similar to those for signal 2LA, above referred to, and that if a train moving from right to left is approaching in a section at the right of section I2T, signal 4RA will be at stop and consequently signal ZRA will be at caution. The circuit for mechanism ZRAG may be traced in Figs. 3B and 3A from terminal B, back contact 29 of relay 4RAP, front contact 30 of relay INWP, mechanism 2RAG-, contacts l6,-l1, l9, 3|, 21, 28, 32, 33, 34, 35, 36, contact l! of a stick relay 4ABS, contact I52 of relay 4LAR, back contacts I53 and 38 of relays 4LS and 4RAP to terminal C.

Since signal 2LA is at stop, relay ZLAP is deenergized and the circuit for mechanism 4LAG similar to the one for mechanism 2RAG just traced is in a similar condition and signal 4LA is at caution. That is, when two trains are approaching the same siding from opposite directions but neither has entered the adjacent approach Zone, the two entering signals QRA and the. will both indicate caution. Relay lLAS is therefore released, but its contact 3% which governs the circuit for mechanism ZRAG under the active condition as in the first form of the appa-,

ratus is now bridged by contact lhl of a relay tABS which relay is energized over contact l54 of relay GAB, as shown in Fig. 3B. The corresponding open contact til of relay ZRAS in the circuit for mechanism iLAG is similarly bridged by contact 655 of relay EABS, which relay is energized over contact act of relay 2A3.

If new the train approaching signal 2RA at caution enters section MT in Fig. 1C at the left of- Fig. 3A before the train approaching signal 411A at caution enters section EZT, in Fig. 1C at the right of Fig. 38, signal lLA will be put to stop and signal 2RA held at caution for the reason that when the train moving from left to right enters section HT, relay ZBAR is released by the opening of contact 83 of relay MTB, thereby opening contact lint of relay QRAR in the circuit for mechanism lLAG. Signal filLA will therefore assume the stop position and back contact E51 of mechanism lLAG will close to bridge contact I152 of relay QLAR to maintain the can-- tion circuit for signal ERA closed after the opposing train approaching the siding from the right occupies section 2.2T, and by opening contact M of relay lZTR releases relay iLAl-l. It follows that the trains in this case will be held at signals ARA and ALA, respectively. It will be seen that the arrangement is such that when two trains are approaching a siding from opposite directions, each will first encounter a caution signal and that adequate stopping distance may be provided to prevent either train from overrunning a stop signal.

Similar conditions prevail with regard to movements through the two sidings at opposite ends of the single track stretch when two trains are approaching these sidings from opposite directions. Considering f rst the siding at the lefthand end of the stretch, and placing Fig. 313 at the right of Fig. 3A, it will be seen that when a train moving from left to right and approaching signal ERA at caution or clear enters section Alll'l, relay SEAR is released by the opening of contact M of relay AlFlTR since relay ERAS is deenergized and contact 98 is open, and if signal l-RA at the left-hand end of the single track stretch is at clear or caution, relay @RAR by opening contact Fig. 3B, in the circuit for mechanism 153G, in Fig. 16 at the right of Fig. 3B, causes the opposing signals l3, M and ZLA at the right of the siding which the train is approaching to assume the stop position. cm the other hand, if signal ARA is at stop, contact E58 'of relay iRAR is bridged by back contact 559 of relay lRAG and the opposing signals are not interfered with by the release of relay QRAR by a train moving from left to right.

Considering next that drawings 3A and 33 represent the siding at the right-hand end of the single track stretch under discussion, it will be seen that when a train moving from right to left and approaching signal iLA at caution or clear enters section AltT, relay ZLAR is released by the opening of contact m2 of relay Al3TR, and if signal ZLA at the right-hand end of the single track stretch is at clear or caution,

relay 2LAR by opening contact I60, Fig. 3A, in the circuit for mechanism IBG, in Fig. 1C at the left of Fig. 3A, causes signals l0, l2 and ZRA at the left of the siding which the train is approaching to assume the stop position, but if signal lLA is at stop, contact ISO is bridged by contact I50 of relay 2LAG, and the opposing signals are not interfered with by the release of relay 2LAR by a train moving from right to left. It will be seen that if two opposing trains approach adjacent sidings simultaneously and the train moving from left to right causes the opposing signal ZLA at the right-hand end of the single track stretch in advance of the siding to assume the stop position before the corresponding relay ZLAR is released by the opposing train, back contact Hit of mechanism ZLAG at the righthand and of the single track stretch will close before contact I60 of relay ALAR opens and the train moving from left to right may continue through the single track stretch and the trains will be held at signals ZRA and ZLA, respectively.

The control limits for the signals in this form of the apparatus are overlapped in this manner when the stations are inactive to prevent trains from simultaneously passing opposing clear signals at the opposite ends of a block and it follows that since the control limits extend further under inactive control than in the first form of the apparatus, a change from inactive to active control involves a shift in the control limits.

It will be assumed that the signals at station No. l are manually put to stop by sending a code to render that station active by the release of RAB, with relays ZRHS and 2LHS remaining deenorgized. Signals ZRA and ZLA will be put to stop by the opening of front contacts H and @535 of relay 2A3 and contacts i552 and iii? of relay RAB will bridge contacts 58%? and 55, respectively, of relays ERAR and 2LAR to cut out the above described overlap in the control limits for signals l0 and iLA, but each of the relays 2RAS QLAS will remain deenergized and its conact or 99 in the control circuit for signal It or :iLA will remain open until relay ZRAS or becomes energized following the return of the a.-sociated signal. ERA or ALA to the stop position. Relay ZABS prevents the temporary opening of the circuits for signals ill and ALA under this condition. Thus after relay 2AB is released and opens its contact H34, relay ZABS is held energized over contact H35 of relay ZLAS and also over contact 656 of relay ERAS, and consequently the circuits for signals ll] and ALA are he" closed at contacts lfil and E55 of relay ZABS M av until these contacts are bridged by contacts 45 and respectively, of relays ZLAS and 2RAS.

The circuits for signals ERA and H3 are controlled in similar manner by relays lAB and 4ABS. It w; beapparent that after relays ZABS and iABS "elease, the opposing signal control is similar to hat hereinbefore described in connection with 1A and 1B and that the second form of the apparatus functions in the same manner as the form when in the active condition.

Although I have herein shown and described but two forms of railway trafiic controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a centralized traffic control system for mally operable to transmit to the control ofilce indications only of certain traflic conditions in response to changes in trafiic conditions at that station, a conditioning relay at each station manually controllable from the control ofiice, and

means controlled by each conditioning relay for Conditioning the transmitting means at the same station to transmit additional indications automatically in response to changes in the condition of the apparatus at such station.

2. In a centralized traflic controlling system for railroads, a control ofiice, a plurality of stations at spaced points along a railway track, a plurality of trafi'ic governing devices at each station, normally inactive apparatus at each station normally operable to transmit to the control ofiice indications only of certain traffic conditions at such station, conditioning means at each station manually controllable from the control ofiice, and

means effective only when said conditioning 25' means is in a given condition to render the apparatus at such station operable to transmit additional indications to indicate the condition of the devices at such station automatically Whenever a change in such condition occurs. 30

3. In a centralized trafi'ic control system for railroads, a control ofiice, a plurality of stations at spaced points along a railway track, a plurality of trafiic governing devices at each station, indication means for such devices at the control office, normally inactive transmitting apparatus at each station, conditioning means manually controllable from the controloffice to selectively render the transmitting apparatus at a selected station active or inactive, means controlled by said transmitting apparatus only when active for automatically controlling the indication means for the devices at such station in accordance with the condition of such devices whenever any change in such condition occurs, and means controlled by each transmitting means for distinc tively controlling the indication means for the devices at the corresponding station to indicate at the office whether such transmitting means is active or inactive.

4. In combination, an oflice and a station, two groups of traffic governing devices at'said station, a transmitter at said station eflective when operated to transmit indications to the oflice indicating the condition of said devices, means 55 operating said transmitter automatically whenever a change in such condition occurs, a conditioning relay, and means controlled by said relay for conditioning said transmitter to transmit indications of one group only of said devices and for rendering said transmitter non-responsive to changes in the condition of the devices of the other group.

5. In combination, an ofiice and a station, a track section at said station, signals for governing trafiic movements over said section, a trans mitter at the station normally efiective when operated to transmit an indication of the condition of said track section to the control office in response to a change in such condition, control relays manually governed from the control ofilce for controlling said signals, a conditioning relay at said station, means efiective when said conditioning relay is in one position for controlling said signals automatically in accordance with traflic conditions without energizing said control relays,

and'means eifective when said conditioning relay is in its other position for selectively conditioning said transmitter to transmit an additional indication during each operation thereof to indicate the condition of said signals at the control oflice. 6. In a centralized trafiic control system for railroads, a control office, a plurality of stations at spaced points along a railway track, a track section at each station, signals at each station for governing traflic movements over such section, indication means at the ofiice for each station for indicating the condition of the track sections and-signals,a transmitter at each station normally effective when operated to transmit an indication of the condition of the track sectionat such station to the ofilce in response to a change in such conditions, control relays at each station manually governed from the cffice for controlling the signals, a conditioning relay at each station, means effective when the conditioning relay at a station is in one position for controlling the signals automatically in accordance with trafiic conditions without energiz ing the control relays at such station, means effective when the conditioning relay at a station is in its other position for selectively conditioning the associated transmitter to control the indication means for the signals at such station in accordance with the condition of such signals to indicate that such signals are subject to manual control, and means at the office for selectively controlling said conditioning relays.

I 7. In combination, a stretch of railway track comprising a plurality of successive track sections a trackrelay for each section, signals at spaced points in said stretch, control circuits controlled by said track relays for clearing said signals automatically in accordance with traffic conditions in said stretch, a control ofiice, a control relay for each signal governed from the ofiice for imposing manual control upon such signal, transmitting means for each signal for automatically transmitting indications of its condition and of the condition of the adjacent tracksection to the ofiice, means at the ofiice for continuously displaying such indications, a conditioning relay for each signal, means effective when each conditioning relay is operated to a given position for cancelling the indication of the corresponding signal at the office, means effective as long as such conditioning relay remains in said given position for rendering the associated signal automatically responsive to the condition of its control'circuit without energizing its control relay and for also preventing the transmission of indications of such signal to the: control ofiice, and means for selectively controlling said conditioning relays.

8. In combination, a stretch of railway track comprising a plurality of successive track sections, a track relay for each section, signals at. spaced 'points in said stretch, control circuits controlled by said track relays for clearing said signals automatically in accordance with trafiic conditions in saidstretch,'a control oflice, a control relay for each signal governed from the ofiice for imposing manual'control upon such signal, a conditioning relay for each signal, means effective only when a conditioning relay is in a given position for rendering the associated signal automatically responsive to the condition of its control circuit without energizing its control relay, and means including the control relays and manuallycontrollable from the control office for selectively controlling said conditioning relays.

9. In combination, a stretch of railway track having a track switch at each end, signals at the ends of the stretch for governing trafiic movements over the stretch, circuits for clearing said signals in accordance with the position of said track switches, a control oflice, a control relay for each signal governed from said onice for imposing manual control upon said signals, means governed from the control oflice for controlling each track switch, a conditioning relay at each end of the stretch, means effective only when a conditioning relay is in a given position for rendering the associated signal automatically responsive to the condition of its control circuit without energizing its respective control relay, means manually controllable from the control office for selectively controlling said conditioning relays, and means preventing the operation of each conditioning relay except when the associated track switch is in a given position.

10. In combination, a stretch of single track railway including a block section, signals at the ends of said block section for governing trafiic movements through said section, a locking relay for each signal energized only when such signal indicates stop, an approach relay for each signal energized only when an adjacent portion of the stretch in the rear of such signal is unoccupied, a control relay for each signal, means for manually governing each control relay, a circuit for clearing each signal controlled by a front contact or" its control relay and by a front contact of the locking relay for the signal at the other end of the block section, a conditioning relay for each signal, means controlled by each conditioning relay in its operated position for completing the circuit for the associated signal in response to the release of the approach relay for such signal without energizing the control relay for such signal, and means for selectively controlling said conditioning relays.

11. In combination, a stretch of railway track having a track switch at each end, two signals including one at each end of the stretch for governing trafiic movements through the stretch, a locking relay for each switch which when deenergized prevents operation of the switch, means for energizing each locking relay efiective only when the associated signal is at stop, a manually governed control relay for each signal, a circuit for each signal governed by its control relay in accordance with the position of the adjacent track switch and closed only when the locking relay for the switch at the opposite end of the stretch is energized, a manually controllable conditioning relay at each end of the stretch, and means controlled by each conditioning relay when in a given position for completing the circuit for the signal at the same end of the stretch to permit such signal to clear without energizing its control relay when a train is approaching within a predetermined distance of such signal.

12. In combination, a stretch of single track railway having a track switch at each end, a main line signal and a siding signal at each end of the stretch for governing trafiic movements from a main line section and from a siding, respectively, into said single track stretch, a locking relay for each switch which when deenergized prevents operation of the switch, means for energizing each locking relay effective only when the asociated signals are at stop, manually governed control relays for said signals, a circuit for each signal governed by its control relay in accordance with the position of the adjacent track switch and closed only when the locking relay for the switch at the opposite end of the stretch is energized, a manually controllable conditioning relay at each end of the stretch, and means controlled by each conditioning. relay when in a given position for completing the circuit for the main line signal at the same end of said stretch to permit each such signal to be cleared automatically by an approaching train without energizing its control relay provided there is no opposing train approaching within a predetermined distance of the other main line signal.

13. In combination, a stretch of single track railway including a block section, signals at the ends of said block section for governing trafiic movements through said section, a locking relay for each signal energized only when such signal indicates stop, an approach relay for each signal energized only when an adjacent portion of the stretch in the rear of such signal is unoccupied, a circuit for clearing each signal controlled in accordance with tranic conditions in said block section, and means effective under one condition for closing the circuit for each signal provided the approach relay for the signal at the other end of the block section is energized and effective under another condition provided the locking relay for the signal at the other end of the block section is energized.

14. In combination, a stretch of single track railway including a block section, signals at the ends of said block section for governing traflic movements through said section, a locking relay for each signal energized only when such signal indicates stop, an approach relay for each signal energized only when an adjacent portion of the stretch in the rear of such signal is unoccupied, a control relay for each signal, means for manually governing each control relay, a circuit for clearing each signal controlled by a front contact of its control relay and by a front contact of the locking relay for the signal at the other end of the block section, a conditioning relay for each signal, means controlled by each conditioning relay in its energized position for completing the circuit for the associated signal without energizingthe control relay for such signal or the locking'relay for the other signal provided the approach relay and the'conditioning relay for the other signal are both energized,'and means for selectively controlling said conditioning relays.

15. In combination, a stretch of single track railway including a block section, signals at the ends of said block section for governing traffic movements through said section, a locking relay for each signal energized only when such signal indicates stop, an approach relay for each signal energized only when an adjacent portion of the stretch in the rear of such signal is unoccupied, a control relay and a conditioning relay for each signal, means for manually governing-each control relay and conditioning relay, means for clearing each signal when its control relay and the lock' ing relay for the other signal are both energized and the conditioning relays for both signals are in a first position, and means for clearing each signal without energizing its control relay when the approach relay for the other signal is energized and the conditioning relays for both signals are in a second position.

16. In combination, a stretch of singleitrack railway including a block section and an ap proach zone at each end of said block section, signals at the ends of said block section for governing traffic movements through said section, a control relay, a conditioning relay and a locking relay for each signal, means for manually governing each control relay and conditioning relay, means for energizing each locking relay only when the associated signal is at stop, means effective when the conditioning relays at the two ends of the stretch are in one position for clearing each signal automatically provided the block section and the approach zone at the end remote from such signal are both unoccupied, and means effective when said conditioning relays are in another position for clearing each signal manually in accordance with trafiic conditions in'said block section provided the locking relay at the end remote from such signal is'energized.

17, In combination, a stretch of single track railway including a block section and an approach zone ateach end of said block section,

signals at the ends of'said block section for governing traflic movements through said section, a control relay, a conditioning relay and a looking relay for each signal, means for manually governing each control relay and conditioning relay, means for energizing each locking relay only when the associated signal is at stop, means effective when the conditioning relays at thetwo ends of the stretch are'in one position for clearing each signal automatically provided the block section and the approach zone at the end remote from such signal are both unoccupied, means eifective when said conditioning relays are in another position for clearing each signal manually in accordance with traffic conditions in said block section provided the locking relay at the end remote from such signal is energized, and means efiective when each conditioning relay assumes such other position for rendering the associated locking relay ineffective to control the signal at the other end of the block section until such locking relay becomes energized.

18. In combination, a stretch of railway track including a block section and an adjacent approach section, a signal for governing traffic movements from said approach section into said block section, a control relay for imposing manual controlupon said signal, a manually controlled conditioning relay, an approach relay energized only when said approach section is unoccupied, a circuit for clearing said signal controlled in accordance with traffic conditions in said block section and closed when said control relay is energized provided said block section is unoccupied and said conditioning relay is in one position, and means effective when said conditioning relay is in another position and said control relay is deenergized for closing said circuit automatically in response to the release of said approach relay by a train approaching said signal.

19. In combination, a stretch of railway track including a block section and an adjacent approach section, a signal for governing trafiic movements from said approach section into said block section, a control relay for imposing manual control upon said signal, a manually controlled conditioning relay, an approach relay energized only when said approach section is occupied, a directional stick relay, means for energizing said stick relay as long as said approach section is occupied by a train moving away from said block section, a control circuitfor clearing said signal controlled in accordance with tr'afiic conditions in said block section and closed when said control relay is energized provided said block section is unoccupied and said conditioning relay is in one position, and means effective when said conditioning relay is in ansection, an approach relay which becomes deenergized when said approach section is'occupied, a stick relay, a pickup circuit for said stick relay controlled by a back contact of said track relay, a stick circuit for said stick relay controlled by a back contact of said approach relay,

, and a control circuit for said signal controlled by a front contact of said track relay and back contacts of said approach relay and of said stick relay.

21. In a centralizedtraffic control system for railroads, a stretch of single track railroad including a plurality of passing sidings each having a power operated track switch at each end, signals at spaced points in said stretch for governing traffic movements through said stretch in both directions, a communication system for effecting manual control of said switches and signals comprising a plurality of field stations connected with a control. oflice by line wires, each field station being adjacent a different track switch, a plurality of track sections in said stretch each having a track relay, signal control circuits for said signals controlled by said track relays and normally efi'ective to clear said signals automatically to permit train movements through said stretch in one direction or the other over the track switches in their normal position, means for automatically initiating the operation of said communication system to transmit indications of train movements through each track section in said stretch which includes a track switch and also to indicate the position of any track switch which becomes displaced from its normal position, means including said communication system for selecting a particular field station and for controllingthe track switch and signals ad'- jacent such switch manually from the control office, and means for automatically initiating the operation of said communication system to transmit indications of the clear and stop positions of said manually controllable signals to said control ofiice efiective only so long as said signals are being controlled manually.

22. In combination, a detector section of railway track including a track switch, approach sections adjoining the ends of said detector section, a signal at each end of said detector section for governing traflic movements from the adjacent approach section into said detector section, a circuit for clearing each signal controlled in accordance with the position of the track switch and closed only when the detector section and the approach section at the end thereof remote from such signal are unoccupied and the opposing signal is at stop, a directional stick relay for each signal, a pickup circuit for each stick relay closed when said detector section becomes occupied provided the associated signal is then clear and the opposing signal and its stick relay are deenergized, an approach relay for each signal energized only when the approach section adjacent such signal is unoccupied, stick circuit means for holding the stick relay for each signal energized as long as said detector section is occupied or the approach relay for the opposing signal is deenergized, and means for automatically closing the circuit for each signal comprising back contacts of the approach relay for such signal and of the stick relay for the opposing signal.

23. In combination, a detector section of rail- Way track including a track switch, approach sections adjoining the ends of said detector section, a signal at each end of said detector section for governing trafiic movements from the adjacent approach section into said detector section, a circuit for clearing each signal controlled in accordance with the position of the track switch and closed only when the detector section and the approach section at the end thereof remote from such signal are unoccupied and the opposing signal is at stop, a directional stick relay for each signal, a pick-up circuit for each stick relay closed when said detector section becomes occupied provided the associated signal is then clear and the opposing signal and its stick relay are deenergized, an approach relay for each signal energized only when the approach section adjacent such signal is unoccupied, stick circuit means for holding the stick relay for each signal energized as long as said detector section is occupied or the approach relay for the opposing signal is deenergized, means for automatically closing the circuit for each signal to permit an approaching train to enter said detector section, a marker lamp associated with each signal, and means controlled by each stick relay when energized for lighting the marker lamp for the associated signal to indicate the direction of movement of said train after it has passed said signal.

24. In combination, a detector section of railway track including a track switch, approach sections adjoining the ends of said detector section, a signal at each end of said detector section for governing trafiic movements from the adjacent approach section into said detector section, a circuit for clearing each signal controlled in accordance with the position of the track switch and closed only when the detector section and the approach section at the end thereof remote from such signal are unoccupied and the opposing signal is at stop, a directional stick relay for each signal, a pickup circuit for each stick relay closed when said detector section becomes occupied provided the associated signal is then clear and the opposing signal and its stick relay are deenergized, an approach relay for each signal energized only when the approach section adjacent such signal is unoccupied, stick circuit means for holding the stick relay for each signal energized as long as said detector section is occupied or the approach relay for the opposing signal is deenergized, a manually controlled conditioning relay, means effective when said conditioning relay is in one position for manually closing the circuits for said signals to clear one signal or the other, means effective when said conditioning relay is in another position for automatically closing the circuit for each signal comprising back contacts of the approach relay for such signal and of the stick relay for the opposing siganl, a marker lamp associated with each signal, and means controlled by said conditioning relay in said another position and by each stick relay when energized for lighting the marker lamp for the associated signal.

EARL M. ALLEN. 

